Department of Microtechnology and Nanoscience , Chalmers University of Technology , Gothenburg 41296 , Sweden.
Department of Physics and Astronomy, Materials Theory Division , Uppsala University , Box 516 , SE-75120 Uppsala , Sweden.
ACS Appl Mater Interfaces. 2018 Dec 5;10(48):41738-41746. doi: 10.1021/acsami.8b10033. Epub 2018 Nov 20.
The electrical contact resistance at metal-graphene interfaces can significantly degrade the properties of graphene devices and is currently hindering the full exploitation of graphene's potential. Therefore, the influence of environmental factors, such as humidity, on the metal-graphene contact resistance is of interest for all graphene devices that operate without hermetic packaging. We experimentally studied the influence of humidity on bottom-contacted chemical-vapor-deposited (CVD) graphene-gold contacts, by extracting the contact resistance from transmission line model (TLM) test structures. Our results indicate that the contact resistance is not significantly affected by changes in relative humidity (RH). This behavior is in contrast to the measured humidity sensitivity [Formula: see text] of graphene's sheet resistance. In addition, we employ density functional theory (DFT) simulations to support our experimental observations. Our DFT simulation results demonstrate that the electronic structure of the graphene sheet on top of silica is much more sensitive to adsorbed water molecules than the charge density at the interface between gold and graphene. Thus, we predict no degradation of device performance by alterations in contact resistance when such contacts are exposed to humidity. This knowledge underlines that bottom-contacting of graphene is a viable approach for a variety of graphene devices and the back end of the line integration on top of conventional integrated circuits.
金属-石墨烯界面的接触电阻会显著降低石墨烯器件的性能，目前这一问题也阻碍了石墨烯潜力的充分发挥。因此，对于那些没有密封包装而工作的所有石墨烯器件来说，环境因素（如湿度）对金属-石墨烯接触电阻的影响是非常重要的。我们通过从传输线模型（TLM）测试结构中提取接触电阻，实验研究了湿度对底部接触化学气相沉积（CVD）石墨烯-金接触的影响。我们的结果表明，接触电阻受相对湿度（RH）变化的影响不大。这种行为与所测量的石墨烯片电阻的湿度灵敏度 [Formula: see text] 形成对比。此外，我们还采用密度泛函理论（DFT）模拟来支持我们的实验观察。我们的 DFT 模拟结果表明，与金和石墨烯之间的界面电荷密度相比，顶部二氧化硅上的石墨烯片的电子结构对吸附水分子更为敏感。因此，我们预测当这些接触暴露于湿度时，接触电阻的变化不会导致器件性能下降。这一认识突出表明，对于各种石墨烯器件以及传统集成电路顶部的后端集成，底部接触石墨烯是一种可行的方法。
